English names: Phomopsis cranker and dieback
Nordic names: Blåbærkræft (DK)
Major host plants
Diaporthe vaccinii is restricted to cultivated Vaccinium species. The principal hosts are American and European cranberries (Vaccinium macrocarpon and V. oxycoccus) and blueberries (V. corymbosum). The wild European species V. oxycoccos which usually occurs in mountain bogs could be a potential reservoir for the pest.
Infection starts in succulent current-year shoots. Infected leaves show spots enlarging to 1 cm. The shoots are covered with minute lesions and wilt within 4 days. The wilting spreads downward killing major branches and often the entire plant. Cankers in the stem are long and narrow and covered by bark or epidermis. Pycnidia appear from August to October on dead stems and leaves. Infected fruits turn reddish-brown, soft, mushy, often splitting and causing juice to leak.
No pictures are available.
D. vaccinii is widely distributed in North America. Few occurrences are reported from Lithuania, and the disease has been found but not established in Romania, England and Scotland.
A map can be downloaded from EPPO's website. See instructions here.
The fungus overwinters on infected and dead twigs and possibly on dead twigs, leaves and fruits on the ground. D. vaccinii grows well over a temperature range of 4-32°C with the most favourable temperature for conidia germination and growth at 21-24°C. Conidia enter through wounds or directly into the tips of young, succulent blueberry shoots. The fungus is believed to spread through the vascular tissue and progress downwards towards the base, girdling the branches at their junction, and killing part of the plant above the girdle. The fungus may also remain dormant until favourable conditions permit it to resume growth. Spread rate is measured to 5.5 cm in 2 months.
Natural spore dispersal by rain splash only occurs over short distances. Export of infected vines from North America to other countries has been the main source of infection at new sites.
Detection and inspection
Infection can be detected by visual inspection, but symptomless infections may occur.
Pest status and importance
Since it was first reported in the UK over 30 years ago and disappeared without causing any problems, there could be some doubt about its potential importance. However, since commercial production of Vaccinium is now becoming much more important in Europe, it is important to exclude North American Vaccinium pathogens such as D. vaccinii.
Source of information
See further information here:
Author: Jorma Rautapää
Editor: Dorthe Vestergaard